DANBURY -- As many as 285 households will receive letters this week saying that their children will attend a different Danbury public school next fall.

The school district changed the building assignments to manage overcrowding in some schools and take advantage of three new additions that added 18 classrooms.

All-day kindergarten has been phased in over the past two years, but in the fall the remaining schools will implement the initiative, which requires moving students.

The letters were mailed Friday to any families who would be affected by the redistricting, Finance Director Joe Martino said Monday.

Schools Superintendent Sal Pascarella told the Board of Education that in making the changes, the aim was to minimize the number of families disrupted, hold down transportation costs and maintain the racial balance of schools as required by state law.

The goal was to not pick one or two students from a street, but to find clusters so that children in neighborhoods moved together.

The redistricting plan means that about 31 students will move from Mill Ridge Primary to Shelter Rock School; 39 will move from Mill Ridge Primary to Park Avenue; 12 will move from King Street Intermediate to Shelter Rock; 15 will move from King Street Intermediate to Park Avenue; 97 will move from Morris Street to Park Avenue and 46 will move from Ellsworth to Stadley Rough.

"We grandfathered in any students who would be in their culminating year next year," Martino said. "For instance, those who are in fourth grade going into fifth grade and the Mill Ridge second graders who will be going to third grade."

That will be about 15 percent of the total number of students affected, he said.

Those parents have received a different letter that will ask them to send back their choice for their students to either stay in their home school or move on.

But their siblings, if they are not in their culminating grade in the school, will be required to go to the new school, he said.

The redistricting is necessary because adding all-day kindergarten to all schools next year will lead to overcrowding at Ellsworth Avenue, Morris Street and Mill Ridge Primary schools.

The district built additions at Park Avenue, Shelter Rock and Stadley Rough schools that amount to 18 new classrooms.

Ross Haber, a consultant hired by the district to revise the school boundaries, weighed individual school enrollment trends, population changes of neighborhoods in the city, and the racial and ethnic makeup of the elementary schools when redrawing the lines.

Haber told the school board recently that in his research, he found that enrollment stays the same from year to year, even though the children might move around from school to school.

Haber told them that he had a high level of confidence that this plan would hold up for five years.

The most significant proposed change, which had the support of the board, was at Morris Street School, the city's most overcrowded school.